Data collected from the Boston cohort of the Collaborative Perinatal Study (over 8000 subjects studied between 1959 and 1973) are currently being evaluated in regards to blood pressure in the children. Determinants of blood pressure measured at seven years of age are being sought from the mother's blood pressure during pregnancy, a history of toxemia of pregnancy, a number of perinatal and early developmental factors in the child, and behavioral and socioeconomic factors during early life. Preliminary analyses have identified high blood pressure in the mother, prematurity, toxemia of pregnancy, low socioeconomic status and, especially, obesity in the child as factors related to higher blood pressure at seven years of age. A subset of 400 of the original cohort (now 15 to 18 years of age) are being reevaluated at the present time. The resting blood pressure, as well as the blood pressure response to a number of stressful stimuli (cold pressor test, handgrip exercise, psychological stress), are being measured. The young subjects are also undergoing echocardiography to estimate left ventricular mass, contractility, and cardiac output, and are completing questionnaires designed to assess personality type, repressed hostility, and other such parameters.